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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS
General Certificate of Education Advanced Subsidiary Level and Advanced Level
*6631076049*
9701/04
CHEMISTRY
Paper 4 Structured Questions
May/June 2007
1 hour 45 minutes
Candidates answer on the Question Paper.
Additional Materials:
Data Booklet
READ THESE INSTRUCTIONS FIRST
Write your Centre number, candidate number and name on all the work you hand in.
Write in dark blue or black pen.
You may use a pencil for any diagrams, graphs or rough working.
Do not use staples, paper clips, highlighters, glue or correction fluid
DO NOT WRITE IN ANY BARCODES.
Section A
Answer all questions.
Section B
Answer all questions.
For Examiner’s Use
You may lose marks if you do not show your working or if you do not use
appropriate units.
A Data Booklet is provided.
1
At the end of the examination, fasten all your work securely together.
The number of marks is given in brackets [ ] at the end of each question or
part question.
3
2
4
5
6
7
8
9
Total
This document consists of 16 printed pages.
SP (KN) T32180/4
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2
Section A
Answer all questions in the spaces provided.
1
Zinc chloride is one of the most important compounds of zinc. It is used in dry cell batteries,
as a flux for soldering and tinning, as a corrosion inhibitor in cooling towers and in the
manufacture of rayon.
(a) Draw a fully labelled diagram to show how you could use a standard hydrogen electrode
to measure the standard electrode potential, E o, of zinc.
[6]
(b) The electrolysis of zinc chloride can give different electrode products, depending on the
conditions used.
Suggest the products formed at each electrode in the following cases. One space has
been filled in for you.
conditions
product at anode
product at cathode
chlorine
ZnCl2(l)
ZnCl2(concentrated aqueous)
ZnCl2(dilute aqueous)
[3]
(c) Use the following data, together with relevant data from the Data Booklet, to construct a
Born-Haber cycle and calculate a value for the lattice energy of zinc chloride.
standard enthalpy change of formation of ZnCl2
–415 kJ mol–1
standard enthalpy change of atomisation of Zn(s)
+131 kJ mol–1
electron affinity per mole of chlorine atoms
–349 kJ mol–1
lattice energy = ............................................... kJ mol–1 [3]
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(d) Zinc is an essential element for plant and animal life. It is often administered in the form
of a chelate, which is a complex between a metal ion and a polydentate ligand.
For
Examiner’s
Use
The rate of the reaction between zinc ions and the ligand 4-(2-pyridylazo)resorcinol,
PAR, has been studied.
HO
Zn2+ + 2
N
HO
Zn2+
N
N
N
+ 2H+
N
N
–O
HO
PAR
2
Zn-PAR
Both PAR and its zinc complex absorb radiation in the UV-visible region. The figure
below shows their absorption spectra.
1.4
absorbance
1.2
1.0
0.8
0.6
PAR
Zn-PAR
0.4
0.2
0.0
300
400
500
600
700
wavelength / nm
(i)
Devise a suitable experimental technique for studying how the rate of this reaction
varies with [Zn2+(aq)].
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
(ii)
Describe a reaction you could carry out to show that PAR is a phenol.
..................................................................................................................................
..................................................................................................................................
[7]
[Total: 19]
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2
(a) Write an equation showing the reaction that occurs when calcium nitrate, Ca(NO3)2, is
heated.
......................................................................................................................................[1]
(b) Describe and explain the trend in thermal stability of the nitrates of the Group II
elements.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
......................................................................................................................................[3]
(c) Gently heating ammonium nitrate, NH4NO3, in a test tube produces a mixture of two
gases A and B. No residue remains in the tube.
The mass spectrum of gas A contains peaks at m/e (mass number) values of 16, 17
and 18, whereas that of gas B has peaks at m/e values of 14, 16, 28, 30 and 44.
(i)
Identify the peaks in the mass spectra, and suggest the molecular formulae of the
gases A and B.
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
(ii)
Hence suggest an equation for the thermal decomposition of ammonium nitrate.
..................................................................................................................................
[5]
[Total: 9]
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5
3
Carbon forms two stable oxides, CO and CO2. Lead forms three oxides: yellow PbO, black
PbO2 and red Pb3O4.
For
Examiner’s
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(a) Carbon monoxide burns readily in air. Heating black lead oxide produces oxygen gas,
leaving a yellow residue.
(i)
Suggest a balanced equation for each reaction.
..................................................................................................................................
..................................................................................................................................
(ii)
Explain how these two reactions illustrate the relative stabilities of the +2 and +4
oxidation states down Group IV.
..................................................................................................................................
..................................................................................................................................
[3]
(b) Red lead oxide contains lead atoms in two different oxidation states.
(i)
Suggest what these oxidation states are, and calculate the ratio in which they occur
in red lead oxide.
..................................................................................................................................
..................................................................................................................................
(ii)
Predict the equation for the action of heat on red lead oxide.
..................................................................................................................................
When red lead oxide is heated with dilute nitric acid, HNO3, a solution of lead(II) nitrate
is formed and a black solid is left.
(iii)
Suggest an equation for this reaction.
..................................................................................................................................
(iv)
Explain how this reaction illustrates the relative basicities of the two oxidation states
of lead.
..................................................................................................................................
..................................................................................................................................
[5]
(c) Both tin(II) oxide and tin(IV) oxide are amphoteric.
Write a balanced equation for the reaction between tin(II) oxide and aqueous sodium
hydroxide.
......................................................................................................................................[1]
[Total: 9]
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6
4
The following passage is taken from an A level Chemistry text book.
“In an isolated atom, the five d-orbitals have the same energy. In an octahedral complex ion, however,
the presence of the ligands splits the five orbitals into a group of three and a group of two. These two
groups have slightly different energies.”
(a) Use the following sets of axes to draw the shape of one d-orbital in each of the two
groups mentioned above.
[2]
(b) Explain how the presence of the six ligands, L, in [FeL6]3+ splits the 3d orbitals into two
groups of different energy, and explain whether the two-orbital group or the three-orbital
group has the higher energy.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
......................................................................................................................................[3]
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7
(c) The following table lists the colours and energies of photons of light of certain
wavelengths.
wavelength
/ nm
energy of
photon
colour of
photon
400
high
violet
450
↓
blue
500
lower
green
600
↓
yellow
650
low
red
For
Examiner’s
Use
The visible spectra of solutions of two transition metal complexes C and D are shown in
the diagram below.
1.4
absorbance
1.2
1.0
0.8
0.6
D
C
0.4
0.2
0.0
300
400
500
600
700
wavelength / nm
(i)
A list of possible colours for these complexes is as follows.
yellow
red
green
blue
Choose one of these words to describe the observed colour of each solution.
solution C ............................................
(ii)
solution D ................................................
In which complex, C or D, will the energy gap between the two groups of orbitals be
the larger? Explain your answer.
..................................................................................................................................
..................................................................................................................................
[3]
[Total: 8]
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8
5
The following scheme shows some reactions of methylbenzene.
CH3
CH3
I
Cl
CH2Cl
II
F
III
E
CO2H
COCl
IV
G
(a) Suggest reagents and conditions for reactions I to IV.
I ........................................................................................................................................
II .......................................................................................................................................
III ......................................................................................................................................
IV .....................................................................................................................................
[4]
(b) What type of reaction is each of the following?
reaction I ..........................................................................................................................
reaction III ........................................................................................................................
[2]
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9
(c) Compound F can be converted into 2-phenylethylamine in a two-stage process.
Suggest a structure for the intermediate, H, in the box below, and suggest reagents and
conditions for the steps V and VI.
CH2Cl
CH2CH2NH2
V
F
For
Examiner’s
Use
VI
H
reagents and conditions for step V ..................................................................................
reagents and conditions for step VI .................................................................................
[4]
(d) The compounds E, F and G react at different rates with nucleophilic reagents. Draw
structures for the products of each compound with the following reagents.
If no reaction occurs, write “no reaction” in the box.
reagent
compound
cold water
hot NaOH(aq)
E
F
G
[6]
[Total: 16]
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6
Chemists use skeletal or partial-skeletal formulae to represent larger structures. For example
the structure
OH
CH3
CH2
H2C
H
C
C
CH2
H2C
CH
CH2
CH2
may also be represented as follows.
OH
H
CH3
H
Oestradiol is one of the hormones that controls the reproductive cycle in female mammals.
HO
CH3 H
H
H
H
HO
oestradiol
(a) (i)
(ii)
On the above structure of oestradiol, circle one chiral centre.
What is the total number of chiral centres in the oestradiol molecule? .....................
[2]
(b) Complete the following part-structures (which have the -OH groups removed) to show
the products obtained when oestradiol (above) is reacted with the stated reagents.
(i)
sodium metal
CH3
H
H
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11
(ii)
Br2(aq)
CH3
H
H
(iii)
H
NaOH(aq)
CH3
H
H
(iv)
H
CH3COCl
CH3
H
H
(v)
H
hot acidified K2Cr2O7
CH3
H
H
H
[7]
[Total: 9]
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12
Section B – Applications of Chemistry
Answer all questions in the spaces provided.
7
(a) (i)
In a protein, amino acids are joined together by a process called condensation
polymerisation. Addition polymerisation is used in some synthetic polymers, such
as poly(propene).
State two important differences between condensation polymerisation and addition
polymerisation.
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
(ii)
Using the amino acids glycine and alanine shown, draw the displayed formula of
the dipeptide ala-gly, clearly labelling the peptide link.
H
H2N
C
H
CO2H
H2N
H
C
CO2H
CH3
glycine
alanine
[4]
(b) The diagram below shows a section of DNA.
Identify the blocks labelled X, Y and Z.
X
A
Z
Y
X
Y
C
G
Y
X
X
Y
C
G
Y
X ......................................
X
X
Y
Y ......................................
Z ......................................
[3]
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13
(c) The table below shows the 3-base codes used by RNA.
UUU
UUC
UUA
UUG
phe
phe
leu
leu
UCU
UCC
UCA
UCG
ser
ser
ser
ser
UAU
UAC
UAA
UAG
tyr
tyr
stop
stop
UGU
UGC
UGA
UGG
cys
cys
stop
trp
CUU
CUC
CUA
CUG
leu
leu
leu
leu
CCU
CCC
CCA
CCG
pro
pro
pro
pro
CAU
CAC
CAA
CAG
his
his
gln
gln
CGU
CGC
CGA
CGG
arg
arg
arg
arg
AUU
AUC
AUA
AUG
ile
ile
ile
ACU
ACC
ACA
ACG
thr
thr
thr
thr
AAU
AAC
AAA
AAG
asn
asn
lys
lys
AGU
AGC
AGA
AGG
ser
ser
arg
arg
GCU
GCC
GCA
GCG
ala
ala
ala
ala
GAU
GAC
GAA
GAG
asp
asp
glu
glu
GGU
GGC
GGA
GGG
gly
gly
gly
gly
GUU
GUC
GUA
GUG
(i)
met/
start
val
val
val
val
What amino acid sequence would the following base code produce?
(You may use abbreviations in your answer.)
-AUGUCUAGAGACGGGUAA..................................................................................................................................
..................................................................................................................................
(ii)
What would be the effect on the amino acid sequence if a mutation caused the
base G at position 13 in the sequence to be replaced by U?
..................................................................................................................................
..................................................................................................................................
[3]
(d) (i)
Name a disease which results from a genetic defect.
..................................................................................................................................
(ii)
Explain how the genetic defect can bring about your named disease.
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
[3]
[Total: 13]
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8
(a) Electrophoresis can be used to separate amino acids which are produced by the
hydrolysis of a polypeptide.
Using glycine as an example, explain why the result of electrophoresis depends on pH.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
......................................................................................................................................[3]
(b) The diagram below shows the results of electrophoresis in neutral solution. At the start
of the experiment a spot of a solution containing a mixture of amino acids P, Q, R and S
was placed in the middle of the plate. Following electrophoresis the amino acids had
moved to the positions shown in the lower diagram.
before
+
–
after
+
–
P
(i)
Q
R
S
Which amino acid existed mainly as a zwitterion in the buffer solution?
Explain your answer.
..................................................................................................................................
..................................................................................................................................
(ii)
Assuming amino acids R and S carry the same charge when in this buffer solution,
which is likely to be the larger molecule? Explain your answer.
..................................................................................................................................
..................................................................................................................................
[2]
(c) Amino acids may also be separated by using two-dimensional paper chromatography.
This involves putting a spot of the mixture on the corner of a piece of chromatography
paper and allowing a solvent to soak up the paper. The paper is then dried, turned
through 90° and placed in a second solvent. This method gives better separation than a
one solvent method.
(i)
Paper chromatography relies on partition between the solvent applied and another
phase.
What is this second phase? .......................................................
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(ii)
The table below shows the Rf values for some amino acids in two different
solvents.
amino acid
Rf solvent 1
Rf solvent 2
A
0.1
0.2
B
0.0
0.4
C
0.3
0.0
D
0.8
0.9
E
0.6
0.5
For
Examiner’s
Use
Use the grid below to plot the positions of the amino acids after two-dimensional
paper chromatography using solvent 1 followed by solvent 2.
solvent
front
solvent 1
spot applied
here
solvent 2
solvent
front
(iii)
Which amino acid travelled fastest in both solvents? .................................
(iv)
Which amino acid did not move at all in solvent 2? .................................
[5]
[Total: 10]
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9
(a) Graphite and buckminsterfullerene are two structural forms of carbon. By referring to
diagrams of their structures, suggest three differences in their properties.
graphite
For
Examiner’s
Use
buckminsterfullerene
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
......................................................................................................................................[3]
(b) Nano-sized ‘test-tubes’ can be formed from carbon structures.
What is the relationship between the parts of these ‘test tubes’ and the two structural
forms of carbon shown above?
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
......................................................................................................................................[3]
(c) Many modern sunscreens contain nano-sized particles of titanium dioxide. This
substance does not absorb ultraviolet radiation.
Suggest how these nano-particles are able to protect skin from ultraviolet radiation.
..........................................................................................................................................
......................................................................................................................................[1]
[Total: 7]
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